Process for the preparation of porous crystalline lithium-, vanadium and phosphate-comprising materials

ABSTRACT

The present invention relates to a process for the preparation of compounds of general formula (I)
 
Li a-b M 1   b V 2-c M 2   c (PO 4 ) x   (I)
 
wherein M 1 , M 2 , a, b, c and x have the following meanings:
     M 1 : Na, K, Rb and/or Cs,   M 2 : Ti, Zr, Nb, Cr, Mn, Fe, Co, Ni, Al, Mg and/or Sc,   a: 1.5-4.5,   b: 0-0.6,   c: 0-1.98 and   x: number to equalize the charge of Li and V and M 1  and/or M 2 , if present,
 
wherein a-b is &gt;0,
 
to a compound according to general formula (I) as defined above, to spherical agglomerates and/or particles comprising at least one compound of general formula (I) as defined above, to the use of such a compound for the preparation of a cathode of a lithium ion battery or an electrochemical cell, and to a cathode for a lithium ion battery, comprising at least one compound as defined above.

This application is a divisional of U.S. application Ser. No. 12/681,193filed Aug. 18, 2010, which is a National Stage of PCT/EP2008/062427filed Sep. 18, 2008, which claims benefit of 60/976,640 filed Oct. 1,2007 and 61/024,631 filed Jan. 30, 2008, of which all are incorporatedherein by reference.

The present invention relates to a process for the preparation of porouscompounds comprising lithium, vanadium and phosphate, to a process forthe preparation of mixtures comprising these compounds and at least oneelectrically conducting material, to the compounds and the mixtures,preparable by these processes and the use of these compounds andmixtures for the preparation of cathodes of lithium-ion batteries.

Processes for the preparation of Li₃V₂ (PO₄)₃ are already known from theprior art.

U.S. Pat. No. 6,528,033 B1 discloses a method for making compounds likeLi₃V₂(PO₄)₃ in a so-called carbo-thermal procedure. A mixture of V₂O₅,Li₂CO₃ (NH₄)₂HPO₄ and carbon is heated to 300° C. to remove ammonia,water and carbon dioxide, the cooled mixture is powderized andpelletized, and heated in an inert atmosphere to a temperature of 850°C. In the carbo-thermal procedure according to this document carbon isthe agent which is reducing V⁵⁺ to V³⁺.

U.S. Pat. No. 5,871,866 discloses a procedure for the preparation ofLi₃V₂(PO₄)₃ by mixing Li₂CO₃, V₂O₅ and (NH₄)₂HPO₄ in methanol and dryingthis slurry subsequently. The powder obtained therefrom is calcinated ata temperature of 875° C. in pure hydrogen as the reducing agent.

U.S. Pat. No. 5,910,382 discloses a process for the preparation ofLi₃V₂(PO₄)₃ starting from Na₃V₂(PO₄)₃ by exchanging the sodium-ions withlithium-ions.

C. Wurm et al., Chem. Mater. 2002, 14, pages 2701 to 2710, discloseLiM_(x)P₂O₇, in which M is Fe or V which are prepared by mixing solubleprecursor in water, followed by slow evaporation of water and annealingat temperatures of 300 to 800° C. in an atmosphere of nitrogen andhydrogen.

S. Patoux et al., J. Power Sources 119 to 121 (2003), pages 278 to 284,disclose pure monoclinic Li₃M₂(PO₄)₃, wherein M is Fe or V, by initialhomogenization of precursors in aqueous solution followed by slowevaporation of H₂O and volatile species and further annealing of theresulting solid under crystallisation. Annealing is conducted under anatmosphere of nitrogen and hydrogen.

The processes for the preparation of Li₃V₂(PO₄)₃ according to the priorart bear the drawback that an additional reducing agent has to be addedto the reaction mixture or that the calcination step has to be conductedin a reducing atmosphere. Other disadvantages are that if solidcompounds like Li₂CO₃ and V₂O₅ are mixed in solid phase, it is difficultto obtain a mixture having a homogenous dispersion of the different ionsthroughout the whole mixture. In addition, the processes according tothe prior art are not appropriate to prepare the mentioned compounds inparticles or agglomerates having channels going from the outer surfaceinto the interior of the particles or agglomerates, allowing an improvedpenetration of the agglomerates with the electrolyte of the battery andtherewith allowing an improved mass transport into and out of theparticles or agglomerates.

The object of the present invention is to provide a process for thepreparation of lithium-vanadium-phosphates which makes it possible toobtain these compounds in a very homogenously mixed and crystallinestate. Moreover, it is an object of the present invention to provide aprocess enabling a decrease of the usually applied high calcinationtemperature of 800° C. and more to prepare a monophasiclithium-vanadium-phosphate. It is a further object to provide a processleading to a more finely devided material with a narrow sizedistribution of the crystallites, which in general enables an improvedLi-ion diffusivity in the charging and discharging process of the Li-ionbattery. In addition, the power characteristics and additionally thecapacity of a Li-ion battery should be increased by improving the Li-iondiffusivity. In addition, it is an object of the present invention toprovide a process for the preparation of the mentioned compounds whichcan be conducted easily and with only a few reaction steps. A furtherobject of the present invention is to provide a process for thepreparation of lithium-vanadium-phosphates as agglomerates and/orparticles having channels going from the outer surface to the inside ofthe agglomerates and/or particles, in order to make an efficient masstransport possible.

These objects are achieved by a process for the preparation of compoundsof general formula (I)Li_(a-b)M¹ _(b)V_(2-c)M² _(c)(PO₄)_(x)  (I)wherein M¹, M², a, b, c and x have the following meanings:M¹: Na, K, Rb and/or Cs,M²: Ti, Zr, Nb, Cr, Mn, Fe, Co, Ni, Al, Mg and/or Sc,a: 1.5-4.5,b: 0-0.6,c: 0-1.98 andx: number to equalize the charge of Li and V and M¹ and/or M², ifpresent, wherein a-b>0,comprising the following steps

-   (A) providing an essentially aqueous mixture comprising as    substrates at least one lithium-comprising compound, at least one    vanadium-comprising compound, in which vanadium has the oxidation    state +5 and/or +4 and at least one M¹-comprising compound, if    present, and/or at least one M²-comprising compound, if present, at    least one reducing agent which is oxidized to at least one compound    comprising at least one phosphorous atom in oxidation state +5 and    optionally at least one compound being able to generate at least one    gaseous compound and/or at least one precursor of a gaseous    compound,-   (B) drying the mixture provided in step (A), in order to obtain a    solid compound and-   (C) calcining the solid compound obtained from step (B) at a    temperature of 300 to 950° C.,    wherein at least one of the substrates generates at least one    gaseous compound or at least one precursor of a gaseous compound and    the at least one gaseous compound and/or the gaseous compound    generated form the at least one precursor is liberated in step (B)    and/or (C).

In a preferred embodiment, M¹, M², a, b and c have the followingmeanings:

-   M¹: Na,-   M²: Fe, Co, Ni, and/or Al,-   a: 2.0-4.0, particularly preferred 2.5-3.5, specifically preferred    2.75-3.25, for example 2.9-3.1,    b: 0-0.6, particularly preferred 0-0.4, specifically preferred    0-0.2, for example 0.05, if present 0.01-0.6, particularly preferred    0.01-0.4, specifically preferred 0.01-0.2, for example 0.01-0.05,    wherein a-b>0,-   c: 0-1.8, particularly preferred 0 b is 1.0, for example 0-0.5, if    present 0.1-1.8, particularly preferred 0.1 b is 1.0, for example    0.1-0.5.

x is chosen in order to equalize the charge of the compound of generalformula (I), depending on the presence, oxidation state and the amountof Li and V, and optionally being present M¹ and/or M². x has always avalue that, depending on Li and V, and M¹ and M², if present, aneutrally charged compound of general formula (I) is obtained. x canhave values of 1.5 to 4.5.

For example, in a very preferred embodiment, M¹ and M² are absent, and cis 0, which makes x to be 3, in order to have a neutrally chargedcompound of general formula (I) Li₃V₂(PO₄)₃.

In a very preferred embodiment, the process according to the presentinvention is conducted in order to obtain the compound of formulaLi₃V₂(PO₄)₃.

In further preferred embodiment, M¹, being for example Na, is present inan amount of up to 10 mol %, in respect of the sum of L¹ and M¹. Inanother preferred embodiment, M², being for example Fe, Co, Ni, Al, ispresent in an amount of up to 50 mol %, in respect of the sum ofvanadium(III) and M² present in the compound.

Therefore, preferred embodiments of the present invention areembodiments, in which Li is substituted by M¹ in an amount of up to 10mol % in respect of the sum of the amounts of L¹ and M¹, andvanadium(III) is substituted with M² in an amount of up to 50 mol %, inrespect of the sum of the amounts of vanadium(III) and M².

Process steps (A), (B) and (C) are explained in the following in moredetail:

Step (A):

Step (A) of the process according to the present invention comprisesproviding an essentially aqueous mixture comprising as substrates atleast one lithium-comprising compound, at least one vanadium-comprisingcompound, in which vanadium has the oxidation state +5 and/or +4, and atleast one M¹-comprising compound, if present, and/or at least oneM²-comprising compound, if present, at least one reducing agent which isoxidized to at least one compound comprising at least one phosphorousatom in oxidation state +5 and optionally at least one compound beingable to generate at least one gaseous compound and/or at least oneprecursor of a gaseous compound.

In general, all Li-, M²- and M³-comprising compounds known to a personhaving ordinary skill in the art which are able to be incorporated in anessentially aqueous mixture in step (A) of the process can be used inthe process according to the present invention.

In a preferred embodiment the at least one lithium-comprising compoundin step (A) is chosen from the group consisting of lithium hydroxideLiOH, lithium hydroxide-hydrate LiOH*H₂O, lithium acetate LiOAc, lithiumcarbonate Li₂CO₃, lithium nitrate LiNO₃ and mixtures thereof. In a verypreferred embodiment, lithium acetate LiOAc and/or lithiumhydroxide-hydrate LiOH*H₂O and/or lithium nitrate LiNO₃ are used aslithium-comprising compounds in step (A) of the process according to thepresent invention. Particularly preferred lithium acetate LiOAc or acombination of lithium acetate LiOAc and lithium hydroxide-hydrateLiOH*H₂O are used as lithium-comprising compounds in the processaccording to the present invention.

The at least one lithium-comprising compound is added to the mixture instep (A) in the process according to the present invention in aconcentration of in general 0.04 to 3 mol Li/I, preferably 0.2 to 2.0mol Li/I, particularly preferred 0.3 to 1.5 mol Li/I, based on the wholereaction mixture in each case.

In general, all vanadium-comprising compounds in which vanadium has theoxidation state +5 and/or +4, known to a person having ordinary skill inthe art can be used in the process according to the present inventionwhich are able to be incorporated in an essentially aqueous mixture instep (A) of the process. According to the present invention, a singlevanadium-comprising compound in which vanadium has the oxidation state+5, or a mixture of different vanadium-comprising in which vanadium hasthe oxidation state +5 can be used. In addition, a singlevanadium-comprising compound in which vanadium has the oxidation state+4, or a mixture of different vanadium-comprising in which vanadium hasthe oxidation state +4 can be used. It is also possible that a mixtureof different vanadium-comprising compounds can be used in which vanadiumhas the oxidation states +5 and +4, is used.

In a preferred embodiment, the vanadium-comprising compound in whichvanadium has the oxidation state +5 is chosen from the group consistingof vanadium(V)-oxide V₂O₅, ammonium-metavanadate(V) NH₄VO₃,ammonium-polyvanadate and mixtures thereof. Ammonium-polyvanadate is avanadium(V)-oxide, comprising ammonium-cations in an amount of about 5%by weight. Preferred vanadium-comprising compounds in which vanadium hasthe oxidation state +4 are chosen from the group consisting ofvanadyl(IV)sulfate hydrate VOSO₄.xH₂O, vanadium(IV)oxide VO₂ and mixturethereof. x in VOSO₄.xH₂O can have different meanings depending on thedrying state of the compound, for example x is 0, if the compound hasbeen dried completely.

In a preferred embodiment of the present application, at least onevanadium comprising compound is used in which vanadium has the oxidationstate +5.

In a preferred embodiment of the process according to the presentinvention ammonium metavanadate(V) NH₄VO₃ is used as the vanadiumcomprising compound. In this case, NH₃ can be generated from thiscompound during the reaction in the process according to the presentinvention, and gaseous NH₃ can be liberated in step (B) and/or (C). IfNH₄VO₃ is used in combination with LiOAc the compound NH₄OAc is formedduring the reaction in the process according to the present invention,and gaseous NH₄OAc is liberated in step (B) and/or (C). If NH₄VO₃ isused in combination with LiNO₃ the compound NH₄NO₃ is formed during thereaction in the process, and gaseous NH₄NO₃ is liberated in step (B) or(C).

The at least one vanadium-comprising compound is added to the mixture instep (A) in the process according to the present invention in aconcentration of in general 0.04 to 2.0 mol V/I, preferably 0.1 to 1.3mol V/I, particularly preferred 0.2 to 1.0 mol V/I, based on the wholereaction mixture in each case.

The at least one M¹-comprising compound, if present, is chosen from thegroup consisting of sodium hydroxide NaOH, sodium hydroxide-hydrateNaOH*H₂O, sodium acetate NaOAc, sodium carbonate Na₂CO₃, and mixturesthereof. In a very preferred embodiment, sodium acetate NaOAc togetherwith sodium hydroxide NaOH and/or sodium hydroxide-hydrate NaOH*H₂O areused as sodium-comprising compounds in step (A) of the process accordingto the present invention. The preferred sodium-comprising compound issodium acetate NaOAc.

The at least and/or M²-comprising compound, if present, is chosen fromcompounds having the required cation and anion chosen from hydroxide,acetate, oxide, carbonate, halide, like fluoride, chloride, bromide,iodide, and mixtures thereof. In a very preferred embodiment, the anionof the at least one M²-comprising compound is acetate, oxide, hydroxide,carbonate or mixtures thereof.

M¹- and/or M²-comprising compounds are added to the essentially aqueousmixture, if present, in amounts, in which they are present in compoundsof formula (I). A person having ordinary skill in the art knows how tocalculate the required amount.

The process according to the present invention is preferably conductedby introducing at least one reducing agent into the mixture in step (A)of the process according to the present invention, which is oxidized toat least one compound comprising at least one phosphorous atom in anoxidation state +5 during the process according to the presentinvention. The use of at least one reducing agent, which is oxidized toat least one compound comprising at least one phosphorous atom inoxidation state +5 has the advantage that the oxidation product of thisreducing agent gives rise to PO₄ ³″-anions, which are needed in order toobtain the PO₄ ³⁻-comprising compound of general formula (I).

In a preferred embodiment, the at least one reducing agent that isoxidized to at least one compound comprising at least one phosphorousatom in oxidation state +5, is carbon free. According to the presentinvention, carbon free means that no carbon atoms are present in thereducing agent. An advantage of a carbon free reducing agent, likeH₃PO₃, is that the reduction can be conducted at low temperatures like300 or 350° C., whereas carbon as reducing agent makes temperaturesnecessary of 600° C. and higher. These low temperatures make it possibleto obtain nano crystalline materials. Nano crystalline materials can notbe obtained advantageously at high temperatures which are necessary ifcarbon is used as the reducing agent.

In a preferred embodiment, the at least one reducing agent which isoxidized to at least one compound comprising at least one phosphorousatom in a oxidation state +5 is chosen from the group consisting ofH₃PO₃, (NH₄)H₂PO₃, (NH₄)₂HPO₃, (NH₄)₃PO₃, H₃PO₂, (NH₄)H₂PO₂, (NH₄)₂HPO₂,(NH₄)₃PO₂ and mixtures thereof. In a particularly preferred embodimentH₃PO₃, (NH₄)H₂PO₃, (NH₄)₂HPO₃, (NH₄)₃PO₃ and mixtures thereof are used.

The at least one reducing agent which is oxidized to at least onecompound comprising at least one phosphorous atom in oxidation state +5is added to the mixture in step (A) in the process according to thepresent invention in a concentration of in general 0.04 to 2.0 mol P/I,preferably 0.1 to 1.3 mol P/I, particularly preferred 0.2 to 1.0 molP/I, based on the whole reaction mixture in each case.

According to the present invention a combination of at least onereducing agent which is oxidized to at least one compound comprising atleast one phosphorous atom in oxidation state +5 is added to thereaction mixture in step (A) of the process according to the presentinvention. The reducing agent that is used in the process according tothe present invention will preferably be oxidized to PO₄ ³⁻. Because theat least one reducing agent which is oxidized to at least one compoundcomprising at least one phosphorous atom in oxidation state +5 is addedto the reaction mixture in a preferably at least equimolar amount,particularly preferred in an equimolar amount, PO₄ ³⁻ is obtained as theoxidizing product in an amount high enough to be the complete amount ofanion of the compound of general formula (I). According to thisembodiment no compound having at least one phosphorous atom in oxidationstate +5 has to be added.

In another preferred embodiment of the present application theessentially aqueous solution which is provided in step (A) additionallycomprises at least one compound comprising at least one phosphorous atomin oxidation state +5. In this preferred embodiment of the presentinvention a combination of at least one reducing agent which is oxidizedto at least one compound comprising at least one phosphorous atom inoxidation state +5 and at least one compound comprising at least onephosphorous atom in oxidation state +5 is added to the reaction mixturein step (A) of the process according to the present invention. Thereducing agent that is used in the process according to the presentinvention will preferably be oxidized to PO₄ ³⁻. In this embodiment ofthe process according to the present application, PO₄ ³⁻ that isobtained as the oxidizing product is not present in an amount highenough to be the complete amount of anion of the compound of generalformula (I). Therefore, in this embodiment, at least one compound havingat least one phosphorous atom in oxidation stage +5 has to be added.

This at least one compound comprising at least one phosphorous atom inoxidation state +5 will be the second source of PO₄ ³⁻-anions, whichhave to be incorporated into the compound of general formula (I).

Preferred compounds comprising at least one phosphorous atom inoxidation state +5 which are optionally added in step (A) are chosenfrom the group consisting of H₃PO₄, (NH₄)H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄and mixtures thereof. Particularly preferred are H₃PO₄, (NH₄)H₂PO₄,(NH₄)₂HPO₄ and mixtures thereof.

The at least one compound comprising at least one phosphorous atom inoxidation state +5 is optionally added to the mixture in step (A) in theprocess according to the present invention in a concentration of ingeneral 0.02 to 1.0 mol P/I, preferably 0.05 to 0.65 mol P/I,particularly preferred 0.1 to 0.5 mol P/I, based on the whole reactionmixture in each case.

In a further preferred embodiment, in addition to the at least onereducing agent which is oxidized to at least one compound comprising atleast one phosphorous atom in oxidation state +5 and optionally at leastone compound comprising at least one phosphorous atom in oxidation state+5, at least one additional reducing agent is added to the mixture instep (A) of the process according to the present invention. Theadditional reducing agent may also be carbon-free or may contain carbon.The at last one additional reducing agent preferably is chosen fromhydrazine or derivatives thereof, hydroxyl amine or derivatives thereof,reducing sugars, like glucose, saccharose, alcohols like aliphaticalcohols having 1 to 10 carbon atoms like methanol, ethanol, propanols,for example n-propanol or iso-propanol, butanols, for example n-butanol,iso-butanol, ascorbic acid, compounds comprising easily oxidisabledouble bonds, and mixtures thereof.

Examples of derivatives of hydrazine are hydrazine-hydrate,hydrazine-sulfate, hydrazine-dihydrochloride and others. An example of aderivative of hydroxylamine is hydroxyl amine-hydrochloride.Particularly preferred carbon-free reducing agents which are notoxidized to at least one compound comprising at least one phosphorousatom in oxidation state +5 are hydrazine, hydrazine-hydrate, hydroxylamine or mixtures thereof.

The at least one reducing agents which are optionally added are bynature not able to deliver PO₄ ³⁻-anions as oxidation products which canbe incorporated into the compound of general formula (I). Therefore, ifat least one of these additional reducing agents is used, it is alsonecessary to use these reducing agents in combination with at least onecompound comprising which is oxidized to at least one compoundcomprising at least one phosphorous atom in oxidation state +5 andoptionally at least one compound comprising at least one phosphorouscompound in oxidation state +5. In these cases the amount and theconcentrations of the at least one compound which is oxidized to atleast one compound comprising at least one phosphorous atom in oxidationstate +5, optionally at least one compound comprising at least onephosphorous atom in oxidation state +5 and optionally at least oneadditionally reducing agent, which are added in step (A) have to beadjusted accordingly. A person having ordinary skill in the art doesknow how the respective amount has to be calculated.

The at least one additional reducing agent is optionally added to themixture in step (A) in the process according to the present invention ina concentration which depends strongly on the reducing power andreducing potential of this agent. A person having ordinary skill in theart does know how the respective amount has to be calculated.

If a combination of at least one reducing agent which is oxidized to acompound comprising at least one phosphorous compound in oxidation stage+5, preferably H₃PO₃, and at least one compound comprising at least onephosphorous atom in oxidation stage +5, preferably H₃PO₄, is added instep (A) of the process according to the present invention, thiscombination is preferably added in a ratio, for example, H₃PO₃/H₃PO₄,which is larger than the ratio that is necessary to obtain the desiredcompound according to general formula (I). A person having ordinaryskill in the art does know how to calculate the stoichiometric amountsof the components in the mixture of step (A) according to the presentinvention.

In a preferred embodiment, the at least one lithium-comprising compound,the at least one vanadium-comprising compound, in which vanadium has theoxidation state +5 and/or +4, at least one reducing agent which isoxidized to at least one compound comprising at least one phosphorousatom in oxidation state +5, and optionally at least one compoundcomprising at least one phosphorous atom in oxidation state +5, areadded to the essentially aqueous mixture in amounts that are adjusted ina way that the stoichiometry according to general formula (I) isobtained. A person having ordinary skill in the art does know how tocalculate the necessary amounts. In another preferred embodiment of thepresent invention, the at least one lithium-comprising compound is addedin an amount that is ≧1% by weight, preferably ≧2% higher than thestoichiometric amount according to general formula (I).

The mixture which is provided in step (A) of the process according tothe present invention is essentially aqueous. The wording “essentially”in this application has the meaning that more than 80% by weight,preferably more than 90% by weight, particularly preferably more than95% by weight of the solvent, which is used to provide the essentiallyaqueous mixture in step (A) of the process according to the presentinvention, is water.

In addition to water, further solvents that are miscible with water canbe present. Examples of these solvents are aliphatic alcohols having 1to 10 carbon atoms like methanol, ethanol, propanols, for examplen-propanol or iso-propanol, butanols, for example n-butanol,iso-butanol. According to the present invention, alcohols can be addedas additional reducing agent and/or as additional solvent.

In a very preferred embodiment, the solvent that is used in step (A) ofthe process according to the present invention is water without anyadditional solvents.

The order, in which the different components are added to the solvent ormixture of solvents in step (A), is not determined. In a preferredembodiment, the M¹-comprising compound is added first to the solvent,the vanadium-comprising compound, in which vanadium has oxidation state+5 and/or +4, is added as the second component. The at least onereducing agent and optionally the at least one compound having at leastone phosphorous atom having the oxidation state +5, and optionally theat least one additional reducing agent and optionally at least onecompound being able to generate at least one gaseous compound and/or atleast one precursor of a gaseous compound, are added subsequently.

In a preferred embodiment of the present invention, the mixture obtainedfrom step (A) of the process according to the present invention is anessentially aqueous solution of at least one lithium-comprisingcompound, at least one vanadium-comprising compound, in which vanadiumhas the oxidation state +5 and/or +4, at least one reducing agent whichis oxidized to at least one compound comprising at least one phosphorousatom in oxidation state +5 and at least one compound being able togenerate at least one gaseous compound and/or at least one precursor ofa gaseous compound.

Step (A) can be conducted in all suitable reactors that are known to aperson skilled in the art. Step (A) can be conducted continuously ordiscontinuously.

The temperature, under which step (A) of the process according to thepresent invention is conducted is 10 to 120° C., preferably 60 to 100°C., particularly preferably 70 to 95° C. If temperatures higher than100° C. are used, the reaction mixture has to be present in apressure-resistant reactor, because of the boiling point of water.

In a preferred embodiment the mixture is stirred in step (A) for a timeof 0.1 to 24 hours, particularly preferred 0.5 to 18 hours. The pH-Valueof the mixtures to the end of stirring is in general below pH 11, forexample at 2.0 to 9.0.

Step (A) of the process according to the present invention can beconducted under an inert atmosphere. Examples of inert gases arenitrogen, noble gases like helium or argon. In a preferred embodiment,step (A) is conducted under a nitrogen atmosphere.

Reduction of most of the V⁵⁺ to V⁴⁺ and/or V³⁺ and/or V⁴⁺ to V³⁺ is ingeneral conducted in step (A) and/or step (B) of the process accordingto the present invention. It is further possible that completion ofreduction to V³⁺ occurs in step (C) of the process according to thepresent invention. It is possible that reduction immediately startsafter addition of the reducing agent. It is further possible thatreduction starts after the reaction mixture is heated to an increasedtemperature of 40 to 100° C., preferably 60 to 95° C. In anotherpreferred embodiment, if a combination of two P-comprising compounds isused as the reducing agent, for example H₃PO₃/H₃PO₄, the reductionstarts, when both components are added. In a preferred embodiment atleast 50%, particularly preferred at least 75% of the V⁵⁺ and/or V⁴⁺present in the reaction mixture is reduced to V⁴⁺ and/or V³⁺ in steps(A) and/or (B) of the process according to the present invention.

In a further preferred embodiment at least one additional compound isadded in step (A) of the process according to the present invention thatis gaseous or is a precursor of a gaseous compound that is liberated instep (B) and/or (C) of the process according to the present invention.In this embodiment, the gaseous compound which is liberated in step (B)and/or (C) of the process is a combination of the gaseous compoundderived from at least one of the substrates as mentioned above and thegaseous compound that is additionally added or that is derived from anadditionally added compound. Examples of compounds that can additionallybe added are all compounds that become gaseous under the conditions thatare present in step (B) and/or (C) of the process according to thepresent invention.

In a preferred embodiment of the process according to the presentinvention, at least one additional compound being able to generate atleast one gaseous compound and/or at least one precursor of a gaseouscompound is added in step (A). The compound which is able to generate atleast one gaseous compound is preferably chosen from the groupconsisting of NH₃, preferably in aqueous solution, NH₄-salts andmixtures thereof. In a further preferred embodiment the NH₄-salt ischosen from the group consisting of NH₄NO₃, NH₄NO₂, NH₄Cl,NH₄-carboxylates like NH₄OAc or NH₄-formiate and mixtures thereof.

Further suitable compounds being able to generate at least one gaseouscompound and/or at least one precursor of a gaseous compound are organicsolvents that are miscible with water and which are gaseous under theconditions of step (B) and/or (C), like alcohols having 1 to 8 carbonatoms, like methanol, ethanol, propanols, for example n-propanol,iso-propanol, butanols, for example n-butanol, iso-butanol, polyols, forexample diethylenglycol, propylenglycol, 1,4-butandiol, and furthermonomeric, oligomeric or polymeric organic compounds, likepolyacrylates, polyetherols.

If the optionally additionally added compound which is gaseous under theconditions of step (B) and/or (C) is also an alcohol, the total amountof added alcohols is considered for the essentially aqueous mixture asmentioned above.

Step (B):

Step (B) of a process according to the present invention comprisesdrying the mixture provided in step (A), in order to obtain a solidcompound.

In step (B), the mixture obtained from step (A) is converted into asolid compound. The drying of the mixture provided in step (A) of theprocess according to the present invention can be conducted with allmethods known to a person having ordinary skill in the art and which aresuitable for the removal of water of an aqueous mixture of thecomponents as mentioned above.

Preferred methods for drying the mixture from step (A) in step (B) arespray-drying, freeze-drying or combinations thereof. According to thepresent invention, the drying in step (B) can be conducted only byspray-drying, only by freeze-drying or by a combination of thespray-drying and freeze-drying, in both orders.

Spray-drying is preferably conducted by passing the mixture obtainedfrom step (A) through one or more narrow nozzles, wherein fine drops arebeing obtained which are dried by a stream of hot air or nitrogen.Alternatively the spraying can be achieved via a rotating disc. In apreferred embodiment a stream of hot air or nitrogen is used having atemperature of 100 to 500° C., particularly preferred 110 to 350° C.Spray-drying is normally conducted directly with the mixture of step (A)without any intermediate steps. Spray-drying normally gives rise tospherical agglomerates having an average diameter of <0.5 mm. In orderto obtain spherical agglomerates having a diameter of 10-30 μm, in apreferred embodiment of step (B) diluted solutions can be used andspray-drying of these diluted solutions can be conducted using highpressure nozzles.

In a second embodiment, step (B) of the process according to the presentinvention is conducted by freeze-drying. The sprayed mixture istherefore sprayed into, for example liquid nitrogen. The particlesobtained therefrom can be dried in vacuum at a low temperature.

In a preferred embodiment step (B) of the process according to thepresent invention is conducted under an inert atmosphere. Suitable inertgases are chosen from nitrogen or noble gases like helium or argon. Apreferred inert gas is nitrogen.

The drying in step (B) is conducted in order to obtain a dry solid. In apreferred embodiment, the solids obtained show an amorphous structure inthe X-ray pattern. In a preferred embodiment, the drying in step (B) ofthe process according to the present invention is conducted in order toobtain a solid having an amount of water present in the solid of lessthan 40% by weight, preferably less than 35% by weight, particularlypreferably less than 25% by weight.

In a preferred embodiment, in addition in step (B) of the processaccording to the present invention the at least one gaseous compoundgenerated from at least one substrate and/or the additionally addedgaseous compound are, at least partially, liberated in step (B) of theprocess. Liberating the at least one gaseous compound makes it possibleto obtain channels going from the inside of the generated sphericalagglomerates to the outer surface. This channels are created by the atleast one gaseous compound on their way through the sphericalagglomerate, driven by the increase of volume during evaporation.

In processes according to the prior art, water is in general used assolvent and this water is in every case evaporated into gaseous watersteam in the spray-drying process. This steam in every case willgenerate certain porosity in the agglomerates generated in thespray-drying process. The special target of the process according to thepresent invention is to increase this certain porosity to significantlyhigher values. Therefor substrates being able to decompose to gaseouscompounds within the spray-drying process and/or within or calciningprocess are used. Furthermore, preferably additional additives are usedin the aqueous slurry which induce a larger porosity in the resultingagglomerates during the spray-drying process and/or calcination step bydecomposition in gaseous compounds than the porosity which is induced bythe evaporation of the water itself in the spray-drying and calcinationprocess.

After step (B) the desired solid is present in preferably sphericalparticles having a diameter of 3 to 200 μm, preferably 5 to 100 μm, verypreferably 8 to 50 μm.

Step (C):

Step (C) of the process according to the present invention comprisescalcining the solid compound obtained from step (B) at a temperature of300 to 950° C. Step (C) is preferably conducted at a temperature of 375to 900° C., particularly preferably at a temperature of 400 to 850° C.

Calcination is preferably conducted under an inert gas atmosphere.Examples of inert gases are nitrogen or noble gases like helium and/orargon. In a preferred embodiment, nitrogen is used in step (C) of theprocess according to the present invention.

One advantage of the process according to the present invention is thatcalcination can be conducted under an inert atmosphere and no needexists to conduct step (C) under a reducing atmosphere according to theprior art. Based thereon the process according to the present inventioncan be conducted in a more time and cost saving way. The absence of areducing agent, for example hydrogen, avoids the presence of explosivegaseous mixtures.

Step (C) of the process according to the present invention in general isconducted for a time of 0.1 to 5 hours, preferably 0.5 to 3 hours. In avery preferred embodiment of step (C), the temperature is increasedduring a period of 0.01 to 2 hours, preferably 0.1 to 1.5 hours, then,the temperature is hold for a period of 0.1 to 2 hours, preferably 0.5to 1.5 hours, and at the end the temperature is decreased to roomtemperature.

In a preferred embodiment, the product obtained from step (C) consistsessentially of spherical agglomerates and/or particles having an averagediameter of 3 to 200 μm, preferably 5 to 100 μm, very preferred 8 to 50μm.

In addition to step (B) of the process according to the presentinvention it is further possible that the at least one gaseous compoundgenerated from at least one substrate and/or the additionally addedgaseous compound are, at least partially, liberated in step (C) of theprocess. In another embodiment of the present invention it is possiblethat channels that have already been created in step (B) are furtherenlarged, or new channels are prepared in step (C). In a preferredembodiment of the present invention channels in the particles arecreated in both steps (B) and (C), in a very preferred embodiment mainlyin step (C).

The temperature of calcination has a significant impact onto thespecific surface of the compound according to general formula (I). Ingeneral low temperatures during calcination give rise to high specificsurface area. High temperatures during calcination give usually rise tolow specific surface area. The process according to the presentinvention makes it possible to obtain high surface areas at highcalcination temperatures of 600 to 800° C. The surface area of thecompounds according to the present invention is significantly higherthan the surface area of compounds being prepared in absence of acompound generating a gaseous compound during processing. This findingcan be explained by the generation of very porous agglomerate structureswith high specific surface areas at high calcination temperatures.

The agglomerates and/or particles that are obtained from step (C) of theprocess according to the present invention have in general a specificBET surface area of 0.01 to 50 m²/g, preferably 0.1 to 30 m²/g.

Suitable apparatuses for step (C) are known to the person havingordinary skill in the art, one example is a rotary furnace. Theresidence time in a rotary furnace is based on the inclination and therotating speed of the furnace. A person having ordinary skill in the artdoes know how a suitable residence time is adjusted in the rotaryfurnace. In a preferred embodiment the solid that is calcinated in step(C) of the process according to the present invention is moved duringcalcination, for example in a fluidized bed reactor or in a rotaryfurnace. The solid can also be stirred during calcination.

Step (C) of the process according to the present invention is in generalconducted under a pressure that is suitable that preferably completeconversion into the desired products is obtained. In a preferredembodiment step (C) is conducted under a pressure which is slightlyhigher than atmospheric pressure, in order to prevent oxygen penetratingthe reactor from the outside. This slightly increased atmosphericpressure is preferably caused by at least one inert gas that isstreaming over the solid compound that is calcinated in this step.

The process according to the present invention can be conductedcontinuously or discontinuously. In a preferred embodiment the processaccording to the present invention is conducted discontinuously.

In a preferred embodiment of the process according to the presentapplication, the solid compound obtained from step (B) or from step (C)is milled prior to step (C) and/or after step (C), in order to obtaincrystalline agglomerates and/or particles having the required size.Suitable mills are known to a person having ordinary skill in the art.Examples are jet mills, which supply very low abrasion, preferably underthe use of nitrogen and/or air. In general the channels within theagglomerates or particles are not destroyed in this milling step.

The present invention further relates to a compound according to generalformula (I) as mentioned above, preparable by the process according tothe present invention. The compounds according to general formula (I)preparable by the process according to the present invention showimproved crystallinity compared to compounds prepared by processesaccording to the prior art. In addition the size distribution obtainedis narrower compared to the prior art. The crystallinity of the solidsobtained is improved and the solids obtained have an improved dispersionof ingredients.

In addition, the compounds according to the present invention areobtained in spherical agglomerates and/or particles having channelsgoing from the inside of the agglomerates and/or particles to the outersurface. The present invention therefore further relates to sphericalagglomerates and/or particles comprising at least one compound ofgeneral formula (I) as mentioned above and having channels going fromthe inside of the agglomerates and/or particles to the outer surface.Further characteristic features of these agglomerates and/or particlesare mentioned above.

Because of this fact the compounds of general formula (I) preparable bythe process according to the present invention are particularly suitablefor the use for the preparation of a cathode of a lithium-ion battery oran electrochemical cell. Therefore the present invention also relates tothe use of a compound of general formula (I) preparable by the processaccording to the present invention or a spherical agglomerate and/orparticle according to the present invention for the preparation of acathode of a lithium-ion battery or an electrochemical cell.

The present invention further relates to a cathode for a lithium-ionbattery, comprising at least one compound according to general formula(I) preparable by the process according to the present invention or aspherical agglomerate and/or particle according to the presentinvention. To obtain a cathode as mentioned above the compound accordingto general formula (I) is mixed with at least one electricallyconducting material, described for example in WO 2004/082047.

Suitable electrically conducting materials are for example carbon black,graphite, carbon fibres, carbon nanofibres, carbon nanotubes orelectrically conducting polymers. Typically 2.0 to 40% by weight of theat least one electrically conducting material are used together with thecompound according to general formula (I) in the cathode. To obtain thecathode the electrically conducting material and the compound accordingto general formula (I) are mixed, optionally in the presence of anorganic solvent and optionally in the presence of an organic binder, forexample polyisobutene, and this mixture is optionally formed and dried.A temperature of 80 to 150° C. is applied in the drying step.

In a preferred embodiment the at least one electrically conductingmaterial is added during the preparation of compounds according togeneral formula (I) as mentioned above. In a preferred embodiment, theat least one electrically conducting material is added to the mixture ofthe starting materials in the preparation of the compound according togeneral formula (I).

Therefore, the present invention also relates to a process for thepreparation of a mixture comprising at least one compound according togeneral formula (I) as defined above and at least one electricallyconducting material comprising the following steps

-   (D) providing an essentially aqueous mixture comprising at least one    electrically conducting material, and as substrates at least one    lithium-comprising compound, at least one vanadium-comprising    compound, in which vanadium has the oxidation state +5 and/or +4,    and at least one M¹-comprising compound, if present, and/or at least    one M²-comprising compound, if present, at least one reducing agent    which is oxidized to at least one compound comprising at least one    phosphorous atom in oxidation state +5 and optionally at least one    compound being able to generate at least one gaseous compound and/or    at least one precursor of a gaseous compound,-   (E) drying the mixture provided in step (D), in order to obtain a    solid compound and-   (F) calcining the solid compound obtained from step (E) at a    temperature of 300 to 950° C.,    wherein at least one of the substrates generates at least one    gaseous compound and/or at least one precursor of a gaseous compound    and the at least one gaseous compound and/or the gaseous compound    generated from the at least one precursor of a gaseous compound is    liberated in step (E) and/or (F).

In a preferred embodiment of this process according to the presentinvention, the essentially aqueous solution which is provided in step(D) additionally comprises at least one compound comprising at least onephosphorous atom in oxidation state +5.

The Li-, and optionally M¹- and/or M²-comprising compounds, thevanadium-comprising compounds, the at least one reducing agent which isoxidized to at least one compound comprising at least one phosphorousatom in oxidation state +5, the optionally present at least one compoundcomprising at least one phosphorous atom in oxidation state +5, theoptional at least one compound being able to generate at least onegaseous compound and/or at least one precursor of a gaseous compound,the electrically conductive materials, the apparatuses and the processparameters of the steps (D) to (F) correspond to the ones describedabove. In addition to the at least one reducing agent which is oxidizedto at least one compound comprising at least one phosphorous atom inoxidation state +5 and the optionally present at least one compoundcomprising at least one phosphorous atom in oxidation state +5, at leastone additional reducing agent can be added in a preferred embodiment, asmentioned and defined above.

In a preferred embodiment the electrically conducting material is chosenfrom the group consisting of carbon black, graphite, carbon fibres,carbon nanofibres, carbon nanotubes, electrically conducting polymers ormixtures thereof.

If carbon black, graphite or substances essentially consisting of carbonare used as electrically conducting materials in step (D), thesematerials are preferably suspended in a mixture, preferably anessentially aqueous solution, of the other components. This can beachieved by direct addition of these electrically conducting materialsto the mixture of the other components. Alternatively, carbon black,graphite or substances essentially consisting of carbon can be suspendedin an aqueous solution of hydrogen peroxide, and this suspension canthen be added to a solution of one or more components as mentionedabove. Treatment with hydrogen peroxide normally improves thewettability of carbon with water and makes it possible to obtain carboncontaining suspensions having an improved stability, i.e. having a lowertendency for demixing. In addition the homogenous dispersion of theelectrically conducting material in the mixture is improved.

The process comprising steps (D), (E) and (F) generates agglomeratesand/or particles comprising at least one compound of general formula (I)as mentioned above and at least one electrically conductive materialhaving channels going from the inside of the agglomerates and/orparticles to the outer surface.

The present invention also relates to a mixture, comprising at least onecompound according to general formula (I) as defined above and at leastone electrically conducting material, preparable by a process asmentioned above. In contrast to materials according to the prior art,these mixtures according to the present invention show an improveddispersion of the at least one electrically conducting material in themixture.

The present invention further relates to a agglomerate and/or particlecomprising at least one compound of general formula (I) as defined aboveand at least one electrically conducting material having channels goingfrom the inside of the agglomerates and/or particles to the outersurface. Other characteristics of these agglomerates and/or particlesare mentioned above.

Therefore, the present invention also relates to the use of a mixtureaccording to the present invention or an agglomerate and/or particleaccording to the present invention for the preparation of a cathode of alithium-ion battery or an electrochemical cell.

The present invention also relates to a cathode for a lithium-ionbattery, comprising a mixture according to the present invention or anagglomerate and/or particle according to the present invention.

For the preparation of a cathode using the compound according to generalformula (I) as mentioned above or a mixture comprising the compoundaccording to general formula (I) and at least one electricallyconducting material as mentioned above, in a preferred embodiment thefollowing binders are used:

Polyethyleneoxide (PEO), cellulose, polyethylene, polypropylene,polytetrafluoroethylene, polyacrylonitrile-methylmethacrylate,styrene-butadiene-copolymers,tetrafluoroethylene-hexyluoropropylene-copolymers,polyvinylidenefluoride-hexafluoropropylene-copolymers (PVdF-HFP),perfluoroalkyl-vinylether-copolymers,vinylidenefluoride-chlorotrifluoroethylene-copolymers,ethylene-chlorofluoroethylene-copolymers, ethylene-acrylicacid-copolymers (with and without sodium ions included),ethylene-methacrylic acid (with and without sodium ions included),polyimides and polyisobutene.

The binder is normally added in an amount of 1 to 10% by weight,preferably 2 to 8% by weight, particularly preferred 3 to 7% by weight,in each case based on the whole cathode material.

The mixture comprising at least one compound according to generalformula (I) and at least one electrically conducting material havepreferably a BET surface area of 0.5 to 50 m²/g.

FIGURES

FIG. 1 shows X-ray powder diffraction pattern of the spray-dried powder.The sample is X-ray amorphous.

FIG. 2 shows X-ray powder diffraction pattern of monophasic Li₃V₂(PO₄)₃(isostructural with Li₃Fe₂(PO₄)₃, BET=11.0 m²/g) prepared by calcinationof the amorphous, spray-dried powder (FIG. 1) at 400° C. under nitrogen.

FIG. 3 shows a SEM picture of the surface of an agglomerate with adiameter of about 30 microns prepared by calcination at 700° C.

The present invention is further illustrated by the following examples:

EXAMPLES Example 1

Li₃V₂(PO₄)₃ from LiOH*H₂O, LiCH₃COO, NH₄VO₃, H₃PO₃, H₃PO₄(“stoichiometric”)

(NH₄VO₃ is reduced by H₃PO₃ to V³⁺, H₃PO₃ is oxidized to PO₄ ³⁻ andwater, gaseous NH₄OAc is generated by NH₄ ⁺ and OAc⁻ ions)LiOH*H₂O+2LiOAc+2NH₄VO₃+2H₃PO₃+H₃PO₄=Li₃V₂(PO₄)₃+2NH₄OAc+6H₂O6 l water are placed in a 10-l-glass reactor which is heatable from theoutside at 90° C. under streaming N₂ (50 NL/h). The streaming N₂-coveris maintained during the further reaction. Under stirring 87.48 gLiOH*H₂O (57.49% per weight LiOH, 2.1 mol Li, Chemetall GmbH, D-60487Frankfurt, Germany) and 279.92 g LiCH₃COO (99%, 4.2 mol Li, Chempur,D-76204 Karlsruhe, Germany) are dissolved in these 6 l water which areheated to 90° C. to give a clear solution. 468.15 g NH₄VO₃ (99.95%, 4mol V, H.C. Starck, D-38615-Gosslar, Germany) are dissolved in thissolution to give a clear, lightly yellow aqueous solution. 334.69 gH₃PO₃ (98%, 4 mol P, Acros Organics, B-2440 Geel, Belgium) are dissolvedtherein, whereas a clear, orange-coloured solution is obtained. 230.58 gH₃PO₄ (85%, 2 mol P, Riedel-de-Haen, D-30926 Seelze, Germany) are added.A dark blue-black coloured, aqueous mixture having no visible solids isobtained. This aqueous mixture is stirred under maintaining thestreaming N₂-cover for 16 hours at 90° C. The solution is subsequentlyspray-dried in a spray-dryer (type Minor MM, Niro, Denmark) undernitrogen (inlet temperature=330° C., outlet temperature=106° C.). Thedark-grey spray-powder obtained therefrom shows an amorphous structurein the X-ray powder diffraction pattern (FIG. 1).

50 g of the so-obtained spray powder are heated during one hour to anend temperature T in a continuously rotating (7 rpm) 1-l-sphericalquartz glass in a laboratory rotary furnace (BASF), held at thistemperature T for one hour and is subsequently cooled under streaming N₂to room temperature.

Example 1.1

The end temperature T of 600° C. gives a powder having a BET-surfacearea of 15.2 m²/g and a X-ray powder diffraction pattern showing themonophasic structure of Li₃Fe₂(PO₄)₃, being isostructural withLi₃V₂(PO₄)₃ (FIG. 2). The powder shows a spherical habitus in scanningelectron microscopy (SEM) having an average spherical size of about 30μm. The surface of the sphericals shows small porous channels going intothe interior of the sphericals.

Example 1.2

End temperature T of 700° C. gives a powder having a BET-surface area of11.0 m²/g and a X-ray powder diffraction pattern showing the monophasicstructure of Li₃Fe₂(PO₄)₃, being isostructural with Li₃V₂(PO₄)₃. Thepowder shows a spherical habitus in scanning electron microscopy havingan average spherical size of about 30 μm. The surface of the sphericalsshows small porous channels going into the interior of the sphericals(FIG. 3).

Comparison Example 1

Li₃V₂(PO₄)₃ from LiOH*H₂O, V₂O₅, H₃PO₃, H₃PO₄ (“stoichiometric”)

(V₂O₅ is reduced by H₃PO₃ to V³⁺, H₃PO₃ is oxidized to PO₄ ³⁻ and water)3LiOH*H₂O+V₂O₅+2H₃PO₃+H₃PO₄=Li₃V₂(PO₄)₃+9H₂O

In a 10 l-glass-reactor which is heatable from the outside, 6 l waterare placed at 80° C. under streaming N₂ (50 NL/h). The streamingN₂-cover is maintained during the further process. Under stirring 262.45g LiOH*H₂O (57.49% LiOH, 6.3 mol Li, Chemetall GmbH, D-60487 Frankfurt,Germany) are added and dissolved to give a clear, colourless solution.363.76 g V₂O₅ (99.97%, 2 Mol V₂O₅, GfE Umwelttechnik GmbH, D-90431Nürnberg, Germany) are added. After dissolution of the V₂O₅ a clear,yellow-coloured solution is obtained. 334.69 g H₃PO₃ (98%, 4 mol P,Acros Organics, B-2440 Geel, Belgium) are added to this solution during0.5 minutes. A clear, orange-coloured solution is obtained. 230.58 gH₃PO₄ (85%, 2 Mol P, Fa. Riedel-de-Haen, D-30926 Seelze) are added. Adark blue-black coloured aqueous mixture is obtained, having no visiblesolids. The aqueous mixture obtained is stirred for 16 hours at 90° C.under streaming nitrogen. The solution is subsequently spray-dried undernitrogen in a spray-dryer (type Minor MM, Fa. Niro, Danmark)(temperature at the inlet=330° C., temperature at the outlet=106° C.). Adark-grey spray-powder obtained therefrom shows an amorphous structurein the X-ray powder diffraction pattern.

50 g of the obtained spray powder are subsequently added to acontinuously rotating (7 rpm) 1 l-crystal ball under streaming nitrogen(15 NL/h) in a laboratory rotary furnace (BASF) and heated in one hourto an end temperature T, is hold at this temperature T for one hour andis subsequently cooled to room temperature under streaming N₂.

Comparison Example 1.1

The end temperature T of 600° C. gives rise to a powder having aBET-surface of 0.5 m²/g and a X-ray powder diffraction pattern, showingessentially the monophasic structure of Li₃Fe₂(PO₄)₃ beingiso-structural with the product Li₃V₂(PO₄)₃. Scanning electronmicroscopy shows that the powder has a spherical habitus having a mediumspherical size of about 30 μm.

Comparison Example 1.2

The end temperature T of 700° C. gives rise to a powder having aBET-surface of 0.2 m²/g and a X-ray powder diffraction pattern, showingessentially the monophasic structure of Li₃Fe₂(PO₄)₃ beingiso-structural with the product Li₃V₂(PO₄)₃. Scanning electronmicroscopy shows that the powder has a spherical habitus having a mediumspherical size of about 30 μm.

Example 2

Li₃V₂(PO₄)₃ from LiCH₃COO, NH₄VO₃, H₃PO₃, H₃PO₄, NH₃ (“stoichiometric”)

(NH₄VO₃ is reduced to V³⁺, H₃PO₃ is oxidized to H₃PO₄; NH₄OAc isgenerated from NH₄ ⁺, CH₃COO⁻ and NH₃; additional excess of NH₃ applied)3LiOAc+2NH₄VO₃+2H₃PO₃+H₃PO₄+NH₃=Li₃V₂(PO₄)₃+3NH₄OAc+4H₂O6 l water are placed in a 10-l-glass reactor which is heatable from theoutside at 90° C. under streaming N₂ (50 NL/h). The streaming N₂-coveris maintained during the further reaction. Under stirring 415.74 gLiCH₃COO (99%, 6.3 mol Li, Chempur, D-76204 Karlsruhe, Germany) aredissolved in these 6 l water which are heated to 90° C. to give a clearsolution. 468.15 g NH₄VO₃ (99.95%, 4 mol V, H.C. Starck,D-38615-Gosslar, Germany) are dissolved in this solution to give aclear, lightly yellow aqueous solution. 334.69 g H₃PO₃ (98%, 4 mol P,Acros Organics, B-2440 Geel, Belgium) are dissolved therein, whereas aclear, orange-coloured solution is obtained. 230.58 g H₃PO₄ (85%, 2 molP, Riedel-de-Haen, D-30926 Seelze, Germany) and 156.4 g of an aqueousNH₃-solution (25%, 2.3 mol NH₃, Bernd Kraft, D-47167 Duisburg, Germany)are added. A dark blue-black coloured, aqueous mixture having no visiblesolids is obtained. This aqueous mixture is stirred under maintainingthe streaming N₂-cover for 16 hours at 90° C. The solution issubsequently spray-dried in a spray-dryer (type Minor MM, Niro, Denmark)under nitrogen (inlet temperature=330° C., outlet temperature=106° C.).The dark-grey spray-powder obtained therefrom shows an X-ray amorphousstructure in the X-ray powder diffraction pattern.

50 g of the so-obtained spray-powder are heated during one hour to anend temperature T in a continuously rotating (7 rpm) 1-l-sphericalquartz glass in a laboratory rotary furnace (BASF), held at thistemperature T for one hour and is subsequently cooled under streaming N₂to room temperature.

Example 2.1

The end temperature T of 600° C. gives a powder having a BET-surfacearea of 16.7 m²/g and a X-ray powder diffraction pattern showing themonophasic structure of Li₃Fe₂(PO₄)₃, being isostructural withLi₃V₂(PO₄)₃. The powder shows a spherical habitus in scanning electronmicroscopy having an average spherical size of about 30 μm. The surfaceof the sphericals shows small porous channels going into the interior ofthe sphericals.

Example 2.2

End temperature T of 700° C. gives a powder having a BET-surface area of13.2 m²/g and a X-ray powder diffraction pattern showing the monophasicstructure of Li₃Fe₂(PO₄)₃, being isostructural with Li₃V₂(PO₄)₃. Thepowder shows a spherical habitus in scanning electron microscopy havingan average spherical size of about 30 μm. The surface of the sphericalsshows small porous channels going into the interior of the sphericals.

Example 3

Li₃V₂(PO₄)₃ from LiOAc, NH₄VO₃, N₂H₄*H₂O, H₃PO₃, H₃PO₄, NH₃

formal:2NH₄VO₃+0.5N₂H₄*H₂O=2“NH₄VO_(2.5)”+0.5N₂+3H₂O3LiOAc+2“NH₄VO_(2.5)”+1H₃PO₃+2H₃PO₄+NH₃=Li₃V₂(PO₄)₃+3NH₄OAc+4H₂O

In a 10 l-glass-reactor which is heatable from the outside, 6 l waterare placed at 80° C. under streaming N2 (50 NL/h). The streamingN2-cover is maintained during the further process. Under stirring 415.74g LiCH3COO (99%, 6.3 mol Li, Chempur, D-76204 Karlsruhe, Germany) areadded and dissolved to give a clear, colourless solution. 468.15 gNH4VO3 (99.95%, 4 mol V, H.C. Starck, D-38615-Gosslar, Germany) aredissolved in this solution to give a clear, lightly yellow aqueoussolution. 55.07 g N2H4*H2O (99.95%, 1.1 mol N2H4, Merck, D-64295Darmstadt, Germany) are added to this solution during 15 minutes.Thereupon 167.34 g H3PO3 (98%, 2 mol P, Acros Organics, B-2440 Geel,Belgium) are added to this solution during 0.5 minutes. 461.16 g H3PO4(85%, 4 Mol P, Fa. Riedel-de-Haen, D-30926 Seelze, Germany) and 136.0 gof an aqueous NH3-solution (25%, 2.0 mol NH₃, Bernd Kraft, D-47167Duisburg, Germany) are added. A dark blue-black coloured aqueous mixtureis obtained, having no visible solids. The aqueous mixture obtained isstirred for 16 hours at 90° C. under streaming nitrogen. The solution issubsequently spray-dried under nitrogen in a spray-dryer (type Minor MM,Fa. Niro, Danmark) (temperature at the inlet=330° C., temperature at theoutlet=106° C.). A dark-grey spray powder obtained therefrom shows anamorphous structure in the X-ray powder diffraction pattern.

50 g of the obtained spray powder are subsequently added to acontinuously rotating (7 rpm) 1 l-crystal ball under streaming nitrogen(15 NL/h) in a laboratory rotary furnace (BASF) and heated in one hourto an end temperature T, is hold at this temperature T for one hour andis subsequently cooled to room temperature under streaming N₂.

The end temperature T of 700° C. gives rise to a powder having aBET-surface of 13.4 m²/g and a X-ray powder diffraction pattern, showingessentially the monophasic structure of Li₃Fe₂(PO₄)₃ beingiso-structural with the product Li₃V₂(PO₄)₃. Scanning electronmicroscopy shows that the powder has a spherical habitus having a mediumspherical size of about 30 μm.

Example 4

Li₃V₂(PO₄)₃ from LiOAc, NH₄VO₃, C₆H₁₂O₆ (glucose), H₃PO₃, H₃PO₄, NH₃

formal:2NH₄VO₃+C₆H₁₂O₆(glucose)→2“NH₄VO_(2.5)”+“oxidized glucose”3LiOAc+2“NH₄VO_(2.5)”+1H₃PO₃+2H₃PO₄+NH₃=Li₃V₂(PO₄)₃+3NH₄OAc+4H₂O

In a 10 l-glass-reactor which is heatable from the outside, 6 l waterare placed at 80° C. under streaming N₂ (50 NL/h). The streamingN₂-cover is maintained during the further process. Under stirring 415.74g LiCH₃COO (99%, 6.3 mol Li, Chempur, D-76204 Karlsruhe, Germany) areadded and dissolved to give a clear, colourless solution. 468.15 gNH₄VO₃ (99.95%, 4 mol V, H.C. Starck, D-38615-Gosslar, Germany) aredissolved in this solution to give a clear, lightly yellow aqueoussolution. 217.99 g C₆H₁₂O₆ (Glucose, 99.9%, 1.1 mol C₆H₁₂O₆, Carl RothGmbH & Co., 76185 Karlsruhe, Germany) are added to this solution during15 minutes. Thereupon 167.34 g H₃PO₃ (98%, 2 mol P, Acros Organics,B-2440 Geel, Belgium) are added to this solution during 0.5 minutes.461.16 g H₃PO₄ (85%, 4 Mol P, Fa. Riedel-de-Haen, D-30926 Seelze,Germany) and 136.0 g of an aqueous NH₃-solution (25%, 2.0 mol NH₃, BerndKraft, D-47167 Duisburg, Germany) are added. A dark blue-black colouredaqueous mixture is obtained, having no visible solids. The aqueousmixture obtained is stirred for 16 hours at 90° C. under streamingnitrogen. The solution is subsequently spray-dried under nitrogen in aspray-dryer (type Minor MM, Fa. Niro, Danmark) (temperature at theinlet=330° C., temperature at the outlet=106° C.). A dark-grey spraypowder obtained therefrom shows an amorphous structure in the XRD-powderdiagram.

50 g of the obtained spray powder are subsequently added to acontinuously rotating (7 rpm) 1 l-crystal ball under streaming nitrogen(15 NL/h) in a laboratory rotary furnace (BASF) and heated in one hourto an end temperature T, is hold at this temperature T for one hour andis subsequently cooled to room temperature under streaming N₂.

The end temperature T of 700° C. gives rise to a powder having aBET-surface of 13.8 m²/g and a X-ray powder diffraction pattern, showingessentially the monophasic structure of Li₃Fe₂(PO₄)₃ beingiso-structural with the product Li₃V₂(PO₄)₃. Scanning electronmicroscopy shows that the powder has a spherical habitus having a mediumspherical size of about 30 μm.

Example 5

Li₃V₂(PO₄)₃ from LiOH*H₂O, LiCH₃COO, NH₄VO₃, H₃PO₃LiOH*H₂O+2LiOAc+2NH₄VO₃+3H₃PO₃→Li₃V₂(PO₄)₃+2NH₄OAc

A possible reaction pathway could be:LiOH*H₂O+2LiOAc+2NH₄VO₃+3H₃PO₃=Li₃V₂(PO₄)₃+2NH₄OAc+5H₂O+H₂

6 l water are placed in a 10-l-glass reactor which is heatable from theoutside at 85° C. under streaming N₂ (50 NL/h). The streaming N₂-coveris maintained during the further reaction. Under stirring 87.48 gLiOH*H₂O (57.49% per weight LiOH, 2.1 mol Li, Chemetall GmbH, D-60487Frankfurt, Germany) and 279.92 g LiCH₃COO (99%, 4.2 mol Li, Chempur,D-76204 Karlsruhe, Germany) are dissolved in these 6 l water which areheated to 85° C. to give a clear solution. 468.15 g NH₄VO₃ (99.95%, 4mol V, H.C. Starck, D-38615-Gosslar, Germany) are dissolved in thissolution to give a clear, lightly yellow aqueous solution. 502.04 gH₃PO₃ (98%, 6 mol P, Acros Organics, B-2440 Geel, Belgium) are dissolvedtherein. A dark green-black coloured, aqueous mixture having no visiblesolids is obtained. This aqueous mixture is stirred under maintainingthe streaming N₂-cover for 4 hours at 90° C. The solution issubsequently spray-dried in a spray-dryer (type Minor MM, Niro, Denmark)under nitrogen (inlet temperature=330° C., outlet temperature=106° C.).

50 g of the so-obtained spray powder are heated during one hour to anend temperature T in a continuously rotating (7 rpm) 1-l-sphericalquartz glass in a laboratory rotary furnace (BASF), held at thistemperature T for one hour and is subsequently cooled under streaming N₂to room temperature.

Example 5.1

The end temperature T of 500° C. gives a powder having a BET-surfacearea of 6.0 m²/g and a X-ray powder diffraction pattern showing theX-ray amorphous structure as shown in FIG. 1. The powder shows aspherical habitus in scanning electron microscopy (SEM) having anaverage spherical size of about 30 μm. The surface of the sphericalsshows small porous channels going into the interior of the sphericals.

Example 5.2

The end temperature T of 600° C. gives a powder having a BET-surfacearea of 4.0 m²/g and a X-ray powder diffraction pattern showing themonophasic structure of Li₃Fe₂(PO₄)₃, being isostructural withLi₃V₂(PO₄)₃. The powder shows a spherical habitus in scanning electronmicroscopy (SEM) having an average spherical size of about 30 μm. Thesurface of the sphericals shows small porous channels going into theinterior of the sphericals.

Example 5.3

End temperature T of 700° C. gives a powder having a BET-surface area of1.0 m²/g and a X-ray powder diffraction pattern showing the monophasicstructure of Li₃Fe₂(PO₄)₃, being isostructural with Li₃V₂(PO₄)₃. Thepowder shows a spherical habitus in scanning electron microscopy havingan average spherical size of about 30 μm. The surface of the sphericalsshows small porous channels going into the interior of the sphericals(like FIG. 3).

Example 5.4

End temperature T of 750° C. gives a powder having a BET-surface area of0.5 m²/g and a X-ray powder diffraction pattern showing the monophasicstructure of Li₃Fe₂(PO₄)₃, being isostructural with Li₃V₂(PO₄)₃. Thepowder shows a spherical habitus in scanning electron microscopy havingan average spherical size of about 30 μm. The surface of the sphericalsshows small porous channels going into the interior of the sphericals(like FIG. 3).

The invention claimed is:
 1. A process for the preparation of a mixturecomprising at least one compound according to general formula (I)Li_(a-b)M¹ _(b)V_(2-c)M² _(c)(PO₄)_(x)  (I) wherein M¹, M², a, b, c andx have the following meanings: M¹: Na, K, Rb and/or Cs, M²: Ti, Zr, Nb,Cr, Mn, Fe, Co, Ni, Al, Mg and/or Sc, a: 1.5-4.5, b: 0-0.6, c: 0-1.98and x: number to equalize the charge of Li and V and M¹ and/or M², ifpresent, wherein a-b is >0, and at least one electrically conductingmaterial, said process comprising (D) providing an essentially aqueousmixture comprising at least one electrically conducting material, and assubstrates at least one lithium-containing compound, at least onevanadium-containing compound in which vanadium has the oxidation state+5 and/or +4, and at least one M¹-containing compound, if present,and/or at least one M²-containing compound, if present, at least onereducing agent which is oxidized to at least one compound comprising atleast one phosphorous atom in oxidation state +5 and optionally at leastone compound being able to generate at least one gaseous compound and/orat least one precursor of a gaseous compound, (E) drying the mixtureprovided in (D), in order to obtain a solid compound and (F) calciningthe solid compound obtained from (E) at a temperature of 300 to 950° C.,wherein at least one of the substrates generates at least one gaseouscompound and/or at least one precursor of a gaseous compound and the atleast one gaseous compound and/or the gaseous compound generated fromthe at least one precursor of a gaseous compound is liberated in (E)and/or (F).
 2. The process according to claim 1, wherein the essentiallyaqueous solution which is provided in (D) additionally comprises atleast one compound comprising at least one phosphorous atom in oxidationstate +5.
 3. The process according to claim 1, wherein the at least onereducing agent which is oxidized to at least one compound comprising atleast one phosphorous atom in oxidation state +5 is selected from thegroup consisting of H₃PO₃, (NH₄)H₂PO₃, (NH₄)₂HPO₃, (NH₄)₃PO₃, H₃PO₂,(NH₄)H₂PO₂, (NH₄)₂HPO₂, (NH₄)₃PO₂ and mixtures thereof.
 4. The processaccording to claim 1, wherein the compound which is able to generate atleast one gaseous compound is present and is selected from the groupconsisting of NH₃, NH₄-salts and mixtures thereof.
 5. The processaccording to claim 4, wherein an NH₄-salt is present and is selectedfrom the group consisting of NH₄NO₃, NH₄NO₂, NH₄CI, NH₄OAc, NH₄-formateand mixtures thereof.
 6. The process according to claim 2, wherein theat least one compound comprising at least one phosphorous atom inoxidation state +5 which is added in (A) is selected from the groupconsisting of H₃PO₄, (NH₄)H₂PO₄, (NH₄)₂HPO₄, (NH₄)₃PO₄ and mixturesthereof.
 7. The process according to claim 1, wherein the compound offormula (I) is Li₃V₂(PO₄)₃.
 8. The process according to claim 1, whereinM¹ is present in an amount of up to 10 mol %, in respect of the sum ofLi and M¹.
 9. The process according to claim 1, wherein M² is present inan amount of up to 50 mol %, in respect of the sum of V and M² presentin the compound.
 10. The process according to claim 1, wherein thelithium-containing compound is selected from the group consisting ofLiOH, LiOH*H₂O, LiOAc, Li₂CO₃, LiNO₃ and mixtures thereof.
 11. Theprocess according to claim 1, wherein the lithium-containing compound isLiOAc or a combination of LiOAc and LiOH*H₂O.
 12. The process accordingto claim 1, wherein the vanadium-containing compound has an oxidationstate +5 and is selected from the group consisting of V₂O₅, NH₄VO₃,ammonium-polyvanadate and mixtures thereof, whereinammonium-polyvanadate is a vanadium(V)-oxide, comprisingammonium-cations in an amount of about 5% by weight.
 13. The processaccording to claim 1, wherein the vanadium-containing compound has anoxidation state +4 and is selected from the group consisting of VOSO₄.xH₂O, VO₂ and mixture thereof, wherein x in VOSO₄.x H₂O depends on thedrying state of the compound VOSO₄.
 14. The process according to claim1, wherein the vanadium-containing compound NH₄VO₃.
 15. The processaccording to claim 1, wherein (A) is carried out at a temperature of 70to 95° C.
 16. The process according to claim 1, wherein after (B), thesolid compound is in the form of spherical particles having a diameterof 3 to 200 μm.
 17. The process according to claim 16, wherein thediameter is 8 to 50 μm.
 18. The process according to claim 1, whereinthe product obtained from (C) consist essentially of sphericalagglomerates and/or particles having an average diameter of 3 to 200 μm.19. The process according to claim 18, wherein the diameter is 8 to 50μm.
 20. The process according to claim 1, wherein the electricallyconducting material is selected from the group consisting of carbonblack, graphite, carbon fibres, carbon nanofibres, carbon nanotubes,electrically conducting polymers and mixtures thereof.